chain_operator.py 4.96 KB
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# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
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# Copyright(C) 2013-2018 Max-Planck-Society
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#
# NIFTy is being developed at the Max-Planck-Institut fuer Astrophysik
# and financially supported by the Studienstiftung des deutschen Volkes.

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from __future__ import absolute_import, division, print_function
from ..compat import *
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import numpy as np
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from .linear_operator import LinearOperator


class ChainOperator(LinearOperator):
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    """Class representing chains of operators."""

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    def __init__(self, ops, _callingfrommake=False):
        if not _callingfrommake:
            raise NotImplementedError
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        super(ChainOperator, self).__init__()
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        self._ops = ops
        self._capability = self._all_ops
        for op in ops:
            self._capability &= op.capability

    @staticmethod
    def simplify(ops):
        from .scaling_operator import ScalingOperator
        from .diagonal_operator import DiagonalOperator
        # Step 1: verify domains
        for i in range(len(ops)-1):
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            if ops[i+1].target is not ops[i].domain:
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                raise ValueError("domain mismatch")
        # Step 2: unpack ChainOperators
        opsnew = []
        for op in ops:
            if isinstance(op, ChainOperator):
                opsnew += op._ops
            else:
                opsnew.append(op)
        ops = opsnew
        # Step 3: collect ScalingOperators
        fct = 1.
        opsnew = []
        lastdom = ops[-1].domain
        for op in ops:
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            if (isinstance(op, ScalingOperator) and
                    not np.issubdtype(type(op._factor), np.complexfloating)):
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                fct *= op._factor
            else:
                opsnew.append(op)
        if fct != 1.:
            # try to absorb the factor into a DiagonalOperator
            for i in range(len(opsnew)):
                if isinstance(opsnew[i], DiagonalOperator):
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                    opsnew[i] = opsnew[i]._scale(fct)
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                    fct = 1.
                    break
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        if fct != 1 or len(opsnew) == 0:
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            # have to add the scaling operator at the end
            opsnew.append(ScalingOperator(fct, lastdom))
        ops = opsnew
        # Step 4: combine DiagonalOperators where possible
        opsnew = []
        for op in ops:
            if (len(opsnew) > 0 and
                    isinstance(opsnew[-1], DiagonalOperator) and
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                    isinstance(op, DiagonalOperator)):
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                opsnew[-1] = opsnew[-1]._combine_prod(op)
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            else:
                opsnew.append(op)
        ops = opsnew
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        # Step 5: combine BlockDiagonalOperators where possible
        from ..multi.block_diagonal_operator import BlockDiagonalOperator
        opsnew = []
        for op in ops:
            if (len(opsnew) > 0 and
                    isinstance(opsnew[-1], BlockDiagonalOperator) and
                    isinstance(op, BlockDiagonalOperator)):
                opsnew[-1] = opsnew[-1]._combine_chain(op)
            else:
                opsnew.append(op)
        ops = opsnew
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        return ops

    @staticmethod
    def make(ops):
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        """Build a ChainOperator (or something simpler if possible),
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        a sequence of concatenated LinearOperators.

        Parameters
        ----------
        ops: list of LinearOperator
            Individual operators of the chain.
        """
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        ops = tuple(ops)
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        if len(ops) == 0:
            raise ValueError("ops is empty")
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        ops = ChainOperator.simplify(ops)
        if len(ops) == 1:
            return ops[0]
        return ChainOperator(ops, _callingfrommake=True)
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    @property
    def domain(self):
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        return self._ops[-1].domain
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    @property
    def target(self):
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        return self._ops[0].target
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    def _flip_modes(self, trafo):
        ADJ = self.ADJOINT_BIT
        INV = self.INVERSE_BIT

        if trafo == 0:
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            return self
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        if trafo == ADJ or trafo == INV:
            return self.make([op._flip_modes(trafo)
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                              for op in reversed(self._ops)])
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        if trafo == ADJ | INV:
            return self.make([op._flip_modes(trafo) for op in self._ops])
        raise ValueError("invalid operator transformation")
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    @property
    def capability(self):
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        return self._capability
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    def apply(self, x, mode):
        self._check_mode(mode)
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        t_ops = self._ops if mode & self._backwards else reversed(self._ops)
        for op in t_ops:
            x = op.apply(x, mode)
        return x